Comment on ``Scientific collaboration networks. II. Shortest paths, weighted networks, and centrality"

In this comment, we investigate a common used algorithm proposed by Newman [M. E. J. Newman, Phys. Rev. E {\bf 64}, 016132(2001)] to calculate the betweenness centrality for all vertices. The inaccurateness of Newman's algorithm is pointed out and a corrected algorithm, also with O($MN$) time complexity, is given. In addition, the comparison of calculating results for these two algorithm aiming the protein interaction network of Yeast is shown.Comment: 3 pages, 2 tables, and 2 figure

The Network Analysis of Urban Streets: A Primal Approach

The network metaphor in the analysis of urban and territorial cases has a long tradition especially in transportation/land-use planning and economic geography. More recently, urban design has brought its contribution by means of the "space syntax" methodology. All these approaches, though under different terms like accessibility, proximity, integration,connectivity, cost or effort, focus on the idea that some places (or streets) are more important than others because they are more central. The study of centrality in complex systems,however, originated in other scientific areas, namely in structural sociology, well before its use in urban studies; moreover, as a structural property of the system, centrality has never been extensively investigated metrically in geographic networks as it has been topologically in a wide range of other relational networks like social, biological or technological. After two previous works on some structural properties of the dual and primal graph representations of urban street networks (Porta et al. cond-mat/0411241; Crucitti et al. physics/0504163), in this paper we provide an in-depth investigation of centrality in the primal approach as compared to the dual one, with a special focus on potentials for urban design.Comment: 19 page, 4 figures. Paper related to the paper "The Network Analysis of Urban Streets: A Dual Approach" cond-mat/041124

Networks in Archaeology: Phenomena, Abstraction, Representation

The application of method and theory from network science to archaeology has dramatically increased over the last decade. In this article, we document this growth over time, discuss several of the important concepts that are used in the application of network approaches to archaeology, and introduce the other articles in this special issue on networks in archaeology. We argue that the suitability and contribution of network science techniques within particular archaeological research contexts can be usefully explored by scrutinizing the past phenomena under study, how these are abstracted into concepts, and how these in turn are represented as network data. For this reason, each of the articles in this special issue is discussed in terms of the phenomena that they seek to address, the abstraction in terms of concepts that they use to study connectivity, and the representations of network data that they employ in their analyses. The approaches currently being used are diverse and interdisciplinary, which we think are evidence of a healthy exploratory stage in the application of network science in archaeology. To facilitate further innovation, application, and collaboration, we also provide a glossary of terms that are currently being used in network science and especially those in the applications to archaeological case studies

An Analysis of the Abstracts Presented at the Annual Meetings of the Society for Neuroscience from 2001 to 2006

Annual meeting abstracts published by scientific societies often contain rich arrays of information that can be computationally mined and distilled to elucidate the state and dynamics of the subject field. We extracted and processed abstract data from the Society for Neuroscience (SFN) annual meeting abstracts during the period 2001–2006 in order to gain an objective view of contemporary neuroscience. An important first step in the process was the application of data cleaning and disambiguation methods to construct a unified database, since the data were too noisy to be of full utility in the raw form initially available. Using natural language processing, text mining, and other data analysis techniques, we then examined the demographics and structure of the scientific collaboration network, the dynamics of the field over time, major research trends, and the structure of the sources of research funding. Some interesting findings include a high geographical concentration of neuroscience research in the north eastern United States, a surprisingly large transient population (66% of the authors appear in only one out of the six studied years), the central role played by the study of neurodegenerative disorders in the neuroscience community, and an apparent growth of behavioral/systems neuroscience with a corresponding shrinkage of cellular/molecular neuroscience over the six year period. The results from this work will prove useful for scientists, policy makers, and funding agencies seeking to gain a complete and unbiased picture of the community structure and body of knowledge encapsulated by a specific scientific domain

Effect of ionization, bedding, and feeding on air quality in a horse stable

BACKGROUND: Organic dust is associated with Equine asthma. Ionization should reduce airborne dust levels. OBJECTIVES: To determine the effect of ionization of air, type of bedding, and feed on the levels of airborne dust, endotoxin, and fungal colonies in horse stables. ANIMALS: 24 healthy University-owned horses occupied the stables. METHODS: A randomized controlled cross-over study. Four units with 6 stables were equipped with an ionization installation (25 VA, 5000 Volt Direct Current). Horses were kept either on wood shavings and fed haylage (2 units), or on straw and fed dry hay (2 units). Measurements were performed with and without activated ionization, during daytime and nighttime, repeatedly over the course of a week and repeatedly during 4-6 weeks. Statistical analysis was performed using a mixed effect model with Akaike's Information Criterion for model reduction and 95% profile (log) likelihood confidence intervals (CI). RESULTS: Ionization did not alter concentrations of dust, endotoxin, or fungi, fewer. In the units with straw and hay, the concentration of dust, endotoxin, and fungi (difference in logarithmic mean 1.92 (95%CI 1.71-2.12); 2.86 (95%CI 2.59-3.14); 1.75 (95%CI 1.13-2.36)) were significantly higher compared to wood shavings and haylage. CONCLUSIONS AND CLINICAL IMPORTANCE: The installation of a negative air-ionizer in the horse stable did not reduce concentrations of dust, endotoxin, and viable fungal spores. The substantial effect of low dust bedding and feed is confirmed

Anatomische "Hamstringsehnen" Verankerung mit Interferenzschrauben beim Kreuzbandersatz

Einleitung: Die Verwendung der Hamstringsehnen als Transplantate in der rekonstruktiven Chirurgie des vorderen Kreuzbandes stellt eine wenig invasive Alternative zur herkömmlichen Verwendung des mittleren Patellarsehnendrittels dar. Hier ist jedoch die Transplantatverankerung, die bisher meist extrakortikal, also weit entfernt der nativen Kreuzbandinsertion angelegt wurde problematisch. Hierdurch zeigt das Transplantat-Verankerungs-Konstrukt ein unbefriedigendes elastisches und plastisches Dehnungsverhalten, welches u.A. für eine geringere Kniestabilität und eine gestörte ossäre Transplantatintegration verantwortlich gemacht wird. Eine anatomiegerechte Transplantatverankerung auf Gelenkniveau könnte die mechanischen und biologischen Rahmenbedingungen verbessern, um so die Hamstringsehnen als Alternativtransplantat mit verbesserter klinischer Prognose einsetzten zu können. Eine direkte Verankerung mit Interferenzschrauben erlaubt eine solche anatomische Transplantatverankerung, so dass wir dieses neue Operationsverfahren biomechanisch und tierexperimentell untersucht haben. Methoden: In sechs biomechanischen Teilprojekten und in zwei tierexperimentellen Untersuchungen wurde die Eignung der direkten Verankerung mit biodegradierbaren Interferenzschrauben der Hamstringsehnen im Vergleich zu konventionellen Patellar- und Hamstringsehnen-Techniken untersucht. Ergebnisse: Wir konnten demonstrieren, dass die initiale femorale Verankerungsfestigkeit, auch in Sinne der sog. Hybridfixation ausreichend ist. Die tibiale Verankerung unterliegt jedoch verschiedenen Variablen und bedarf einer differenzierten klinischen Anwendung. Im Vergleich zu konventionellen Techniken der Hamstringsehnen-Verankerung kann das plastische und elastische Dehnungsverhalten durch die Verankerung mit Interferenzschrauben deutlich verbessert werden, wobei jedoch das mechanische Verhalten des Patellarsehnen-Transplantates nicht erreicht wurde. Die tierexperimentelle Analyse zeigt auf, dass die ossäre Integration durch die Kompression des Transplantates auf Gelenkniveau soweit verbessert werden kann, dass sog. Tunnelaufweitungen, als Zeichen einer gestörten Einheilung vermieden werden und, dass das Transplantat mit einer direkten Bandinsertion, entsprechend des nativen vorderen Kreuzbandes, auf Gelenkniveau einheilt. Schlussfolgerung: Die hier vorgelegten Untersuchungen haben erstmals umfassend die Rahmenbedingungen der Interferenzschrauben-Verankerung der Hamstringsehnen beschrieben; einer Technik die inzwischen weltweit verbreitete Anwendung findet. Durch eine anatomische Transplantatverankerung auf Gelenkniveau besteht nun die Möglichkeit, mit optimierten mechanischen und biologischen Rahmenbedingungen eine adäquate Alternativtechnik zur konventionellen Verwendung der Patellarsehnen anzubieten.Introduction: The use of hamstring tendon grafts as a substitute for anterior cruciate ligament reconstruction presents a less invasive procedure compared to the conventional bone-patellar tendon- bone graft. Current techniques of hamstring tendon anterior cruciate ligament reconstruction utilise an extra-cortical fixation. An extra-cortical fixation, however, shows inferior structural parameters with respect to construct slippage or stiffness. These factors may contribute to less stable knees after reconstruction and a delayed osseous integration of the grafted tissue. An anatomic hamstring tendon graft fixation close to the joint line may overcome these problems and may present an alternative to the conventional bone-patellar tendon-bone graft by means of optimised mechanical and biological boundary conditions. We therefore studied anatomic interference fit fixation of hamstring tendon grafts in different mechanical and animal experimental setups. Methods: In six different biomechanical projects and two animal studies, we studied the capability of hamstring tendon interference fit fixation to be used as a secure and reproducible technique of anterior cruciate ligament reconstruction and compared these data to the bone-patellar tendon-bone graft and other conventional hamstring tendon graft fixation techniques. Results: We could demonstrate that the initial femoral fixation strength, as well as a hybrid fixation is sufficient. However, the tibial fixation presents the weak link and underlies different variables, such as bone density and screw geometry. Compared to conventional extra-cortical fixation techniques, the viscoelastic and viscoplastic deformation behaviour could be optimized, but did not reach comparable data to the bone-patellar tendon-bone graft. Animal experiments could clearly demonstrate that interference fit fixation promotes osseous tendon incorporation and minimises the likely hood of a tunnel enlargement. We further found that in contrast to conventional fixation techniques the use of interference screws resulted in the development of a direct ligament insertion anatomy, directly at the joint line, like it is found with the native anterior cruciate ligament. Conclusion: With the present studies we could first describe the mechanical and biological boundary conditions of hamstring tendon interference fit fixation, a technique which gains increased world wide attention as a standard procedure in cruciate ligament surgery. By using an anatomic joint line fixation of hamstring tendon grafts, there are optimised boundary conditions, which therefore presents an adequate alternative to the conventional bone-patellar tendon-bone graft in cruciate ligament reconstruction

Effect of ionization, bedding, and feeding on air quality in a horse stable

BACKGROUND: Organic dust is associated with Equine asthma. Ionization should reduce airborne dust levels. OBJECTIVES: To determine the effect of ionization of air, type of bedding, and feed on the levels of airborne dust, endotoxin, and fungal colonies in horse stables. ANIMALS: 24 healthy University-owned horses occupied the stables. METHODS: A randomized controlled cross-over study. Four units with 6 stables were equipped with an ionization installation (25 VA, 5000 Volt Direct Current). Horses were kept either on wood shavings and fed haylage (2 units), or on straw and fed dry hay (2 units). Measurements were performed with and without activated ionization, during daytime and nighttime, repeatedly over the course of a week and repeatedly during 4-6 weeks. Statistical analysis was performed using a mixed effect model with Akaike's Information Criterion for model reduction and 95% profile (log) likelihood confidence intervals (CI). RESULTS: Ionization did not alter concentrations of dust, endotoxin, or fungi, fewer. In the units with straw and hay, the concentration of dust, endotoxin, and fungi (difference in logarithmic mean 1.92 (95%CI 1.71-2.12); 2.86 (95%CI 2.59-3.14); 1.75 (95%CI 1.13-2.36)) were significantly higher compared to wood shavings and haylage. CONCLUSIONS AND CLINICAL IMPORTANCE: The installation of a negative air-ionizer in the horse stable did not reduce concentrations of dust, endotoxin, and viable fungal spores. The substantial effect of low dust bedding and feed is confirmed